text: // Copyright (c) 2012 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #ifndef MEDIA_AUDIO_AUDIO_OUTPUT_IPC_H_
  #define MEDIA_AUDIO_AUDIO_OUTPUT_IPC_H_
  
  #include <string>
  
  #include "base/memory/unsafe_shared_memory_region.h"
  #include "base/sync_socket.h"
  #include "base/unguessable_token.h"
  #include "media/base/audio_parameters.h"
  #include "media/base/media_export.h"
  #include "media/base/output_device_info.h"
  #include "third_party/abseil-cpp/absl/types/optional.h"
  
  namespace media {
  
  // Contains IPC notifications for the state of the server side
  // (AudioOutputController) audio state changes and when an AudioOutputController
  // has been created.  Implemented by AudioOutputDevice.
  class MEDIA_EXPORT AudioOutputIPCDelegate {
   public:
    // Called when state of an audio stream has changed.
    virtual void OnError() = 0;
  
    // Called when an authorization request for an output device has been
    // completed. The AudioOutputIPCDelegate will delete the AudioOutputIPC, if
    // |device_status| is not OUTPUT_DEVICE_STATUS_OK.
    virtual void OnDeviceAuthorized(OutputDeviceStatus device_status,
                                    const media::AudioParameters& output_params,
                                    const std::string& matched_device_id) = 0;
  
    // Called when an audio stream has been created.
    // See media/mojo/mojom/audio_data_pipe.mojom for documentation of
    // |handle| and |socket_handle|. |playing_automatically| indicates if the
    // AudioOutputIPCDelegate is playing right away due to an earlier call to
    // Play();
    virtual void OnStreamCreated(
        base::UnsafeSharedMemoryRegion shared_memory_region,
        base::SyncSocket::ScopedHandle socket_handle,
        bool playing_automatically) = 0;
  
    // Called when the AudioOutputIPC object is going away and/or when the IPC
    // channel has been closed and no more ipc requests can be made.
    // Implementations should delete their owned AudioOutputIPC instance
    // immediately.
    virtual void OnIPCClosed() = 0;
  
   protected:
    virtual ~AudioOutputIPCDelegate();
  };
  
  // Provides the IPC functionality for an AudioOutputIPCDelegate (e.g., an
  // AudioOutputDevice).  The implementation should asynchronously deliver the
  // messages to an AudioOutputController object (or create one in the case of
  // CreateStream()), that may live in a separate process.
  class MEDIA_EXPORT AudioOutputIPC {
   public:
    virtual ~AudioOutputIPC();
  
    // Sends a request to authorize the use of a specific audio output device
    // in the peer process.
    // If |device_id| is nonempty, the browser selects the device
    // indicated by |device_id|, regardless of the value of |session_id|.
    // If |device_id| is empty and |session_id| is nonzero, the browser selects
    // the output device associated with an opened input device indicated by
    // |session_id|. If no such device is found, the default device will be
    // selected.
    // If |device_id| is empty and |session_id| is zero, the browser selects
    // the default device.
    // Once the authorization process is complete, the implementation will
    // notify |delegate| by calling OnDeviceAuthorized().
    virtual void RequestDeviceAuthorization(
        AudioOutputIPCDelegate* delegate,
        const base::UnguessableToken& session_id,
        const std::string& device_id) = 0;
  
    // Sends a request to create an AudioOutputController object in the peer
    // process and configures it to use the specified audio |params| including
    // number of synchronized input channels.
    // If no authorization for an output device has been previously requested,
    // the default device will be used.
    // Once the stream has been created, the implementation will notify
    // |delegate| by calling OnStreamCreated().
    virtual void CreateStream(
        AudioOutputIPCDelegate* delegate,
        const AudioParameters& params,
        const absl::optional<base::UnguessableToken>& processing_id) = 0;
  
    // Starts playing the stream.  This should generate a call to
    // AudioOutputController::Play().
    virtual void PlayStream() = 0;
  
    // Pauses an audio stream.  This should generate a call to
    // AudioOutputController::Pause().
    virtual void PauseStream() = 0;
  
    // Flushes an audio stream. This should only be called when the stream is
    // paused.
    virtual void FlushStream() = 0;
  
    // Closes the audio stream which should shut down the corresponding
    // AudioOutputController in the peer process. Usage of an AudioOutputIPC must
    // always end with a call to CloseStream(), and the |delegate| passed to other
    // method must remain valid until then. An exception is if OnIPCClosed is
    // called first.
    virtual void CloseStream() = 0;
  
    // Sets the volume of the audio stream.
    virtual void SetVolume(double volume) = 0;
  };
  
  }  // namespace media
  
  #endif  // MEDIA_AUDIO_AUDIO_OUTPUT_IPC_H_
  